A meridional section and a sagittal section of a cylindrical optical element have different focal powers. Therefore, cylindrical optical elements are widely applied to optical systems that produce distorted images. In the civilian field, cylindrical optical elements are usually applied to anamorphic lenses, linear detector lighting, holographic lighting, barcode scanning, optical information processing, among other aspects. In recent years, with rapid development of intense laser systems, synchrotron radiation beamlines, linear test instruments, and the like, people require increasingly high cylindrical precision. However, applications of cylinder are always restricted by optical fabrication and detection technologies. Currently, the optical fabrication technology develops rapidly, but the detection technology to cylinder develops relatively slowly and generally cannot satisfy current application requirements. Therefore, a high-precision detection technology to cylinder becomes a key factor that restricts applications of cylinder. It becomes increasingly urgent to research and develop a high-precision detection technology to cylinder. High-precision detection constitutes the basis and guarantee for high-precision processing of optical elements, and is essential for high-precision processing. High-precision detection to cylinder is required to manufacture a satisfactory high-precision cylinder. However, high-precision detection to the shape of cylinders cannot be implemented by using common detection technologies because of special optical characteristics of the cylinders.
Currently, methods for detecting cylinders include template method, profilometer detection method, auxiliary plane method, optical fiber method, standard cylinder method, and computer-generated holography (CGH) method, wherein the template method and the profilometer detection method are contact detection, and a concave cylinder to be tested is easily scraped, and measurement precision is relatively low. The auxiliary plane method cannot detect an asymmetric deviation of a cylindrical shape. The auxiliary plane method and the optical fiber method are only applicable to cylinders with relatively small diameters. In the CGH method, a hologram needs to be separately designed, made, and computed according to the size and curvature radius of a detected cylinder. Usually, a minimum spacing between scribe lines of holographic gratings is very small, which is difficult to process and it is difficult to ensure precision. In the standard cylinder method, a standard cylinder with very high precision needs to be processed first, and the detection of the standard cylinder is still significantly difficult. Moreover, the shape precision of the standard cylinder directly affects the measurement precision of a cylinder to be detected, which increases the costs of processing and detection.
The standard cylinder method is shown in FIG. 1. A beam of parallel light passes through a standard cylindrical lens 14 configured to generate a cylindrical wave. A part of the light is transmitted. The transmitted light first converges at the center of the curvature of the cylinder to form a linear focal line 2 and then diverges to reach a cylinder 1 to be tested. When the center line of curvature of the cylinder to be tested coincides with a focal line of the standard cylindrical lens, a light wave reflected by the cylinder is used as a detected light wave with shape information of the cylinder. In the figure, a rear surface of the standard cylindrical lens 14 is a standard cylinder having a shape with very high precision. A center line of curvature of the standard cylinder coincides with the focal line of the standard cylindrical lens. A beam reflected by this surface is used as a reference light wave. Interference occurs between the detected light wave and the reference light wave to form an interferogram, and a shape deviation of the detected cylinder is determined according to the interferogram. The standard cylindrical lens is required in the detection method in which relatively high shape quality is required. Consequently, processing is difficult and the cost is high.